問題
Programs often receive JSON such as {"apples": 3, "pears": 5}. Libraries like System.Text.Json parse it for you, but parsing a simple case by hand shows how the format works.
The input is a flat JSON object: {, then zero or more "key": value pairs separated by commas, then }. Keys are quoted and contain no quotes, commas or colons; values are integers, possibly negative. Spaces may appear around any of the symbols.
Implement sum_json_numbers(text).
Input
text: The JSON object.
Output
Return the sum of all values (0 for an empty object).
制約
2 ≤ length of text ≤ 100,000
At most 10,000 pairs; every value and the sum fit in a 64-bit integer
例
入力：
text = "{\"apples\": 3, \"pears\": 5}"
期待される出力：
expected = 8入力：
std::string text = "{\"apples\": 3, \"pears\": 5}";
期待される出力：
long long expected = 8;入力：
string text = "{\"apples\": 3, \"pears\": 5}";
期待される出力：
long expected = 8;解説
3 + 5 = 8.
入力：
text = "{ \"debt\" : -20 , \"cash\":15 }"
期待される出力：
expected = -5入力：
std::string text = "{ \"debt\" : -20 , \"cash\":15 }";
期待される出力：
long long expected = -5;入力：
string text = "{ \"debt\" : -20 , \"cash\":15 }";
期待される出力：
long expected = -5;解説
Spaces around the symbols do not matter: −20 + 15 = −5.
解き方のヒント
まずは自分で考えてから、ヒントを 1 つずつ開いてみましょう。
ヒント 1
Remove the braces, then split the pairs at commas.
ヒント 2
Each value is the text after the colon; trim spaces before converting.
ヒント 3
Use a 64-bit integer and return 0 for an empty object.
目安の計算量
O(length of text) time, O(1) extra space
参考資料
この課題はCodeUtility用に調整されています。上記の説明と制約に従ってください。